Water retention net

ABSTRACT

The present invention provides a water retention net having water retentivity not obtainable in conventional nets, usable suitably, for example, to a vegetation treatment for slopes of arid places or greening treatment of deserts or the like, wherein a water absorbing resin or a water retention agent  10  mainly comprising the water absorbing resin is deposited by a coating means to at least one side of a net prepared by warp knitting, or a steric net in which a string portion  1  forming net meshes  2  has air transmittable and water transmittable gap spaces, for example, a steric structure net prepared by warp knitting, so as to provide water transmittability due to the steric structure and water retentivity due to the water retention agent together, and provide a satisfactory function of supplying water.

TECHNICAL FIELD

The present invention concerns a water retention net which is mainlyutilized, for example, in greening stabilization of slopes or the like,greening treatment of deserts, cultivation of agricultural plants andthe like.

BACKGROUND OF THE INVENTION

Heretofore, in a vegetation treatment with an aim of protection andgreening stabilization of slopes, nets made of metal mesh or syntheticresin materials have been used in which the nets are laid over theslopes to prevent falling of soils and sands and then vegetationmaterials such as seeds and brought-in soils are sprayed.

However, since nets used generally have scarce water retentivity bythemselves and tend to be dried and, accordingly, water required forgrowing plants can not be supplied enough for slopes in little rainfalldistricts or in arid places, so that it has been necessary to appendnon-woven fabrics retaining a water retention agent. Alternatively, ithas been necessary to admix the water retention agent per se, forexample, with brought-in soils.

Further, in recent years, use of steric structure nets in which stringportions forming the net mesh are constituted into a wall or like othersteric structure has been considered in the vegetation treatment with anaim of preventing the vegetation materials from being flushed away orscattered easily by window and rainfall or falling together with soilsand sands (for example, JP-A-03183820(Japanese Patent Laid-Open Hei3-183820)).

However, even in such nets, since constituent yarns are made, forexample, of synthetic resin monofilaments and scarcely have waterabsorbing property by themselves, no sufficient water retention can beprovided by the nets alone.

Further, if the net mesh is made excessively fine, it rather hindersfixation and growing of plants, increases the amount of yarns used,makes the net heavy and difficult to handle with, and expensive as well.

Furthermore, for the greening of deserts, porous pipe materials areburied underground or arranged on the surface of the ground and water ispassed through the pipes to supply water to surface ground layers forinstance. However, this results in problems that control for the amountof water supply is difficult and water supply is localized orpartialized and it is difficult to economize water because of waterevaporation.

Further, while it has been attempted to improve the water retentivity bydirectly mixing, for example, water absorbing resin polymers into soilsand sands of deserts. However, since there is a difference in thespecific gravity between the water absorbing resin polymers and soilsand sands, they are not mixed uniformly but tend to be localized, sothat it is difficult to ensure uniform water retention over the entirearea. Further, since the water absorbing resin polymers are poor in theweather resistance, it is almost impossible to use them for long yearswith no loss of the water retaining effect.

The present invention has been accomplished in view of the foregoingsand intends to provide a water retention net having a water retentivitynot obtainable in conventional nets and capable of being used suitablyto water retention or water absorption in vegetation treatment forslopes, greening treatment for deserts or green treatment of cities,particularly, in steric structure nets as well as in usual nets made ofsynthetic fiber yarns.

DISCLOSURE OF THE INVENTION

The water retention net according to the present invention for solvingthe foregoing subjects comprises a net prepared by warp-knitting inwhich a water absorbing resin or a water retention agent mainlycomprising the resin is deposited to a string portion forming a netmesh.

According to the water retention net of the present invention, since thewater absorbing resin or the water retention agent mainly comprising theresin is deposited to the string portion forming the net mesh, watergiven by spraying or rainfall or water in the ground or air is absorbedand retained in the water retention agent. Particularly, in the netprepared by warp-knitting, since the string portion comprises acontinuous sequence of knit meshes, the water retention agent is easilyretained in the knit mesh opening portion to increase the amount ofwater retained. Further, thus retained water is gradually released.Accordingly, a satisfactory function of supplying water can be providedby laying the net, for example, on the slopes of arid places or wastelands.

The water retention net of the invention is a steric structure net inwhich the string portion forming the net mesh has a steric shape havingair transmittable and water transmittable gap spaces wherein the waterabsorbing resin or the water retention agent mainly comprising the resinis deposited at least on one side substantially over the entire areathereof.

According to the water retention net of the present invention, since thenet constitutes, as a whole, a steric structure having a requiredthickness, it possesses satisfactory air transmittability and watertransmittability by the possession of gap spaces in the steric stringportion. In addition, since the water retention agent is deposited atleast on one side of the net, it has excellent water retentivity in thesame manner as described above. Therefore, when it is laid and used, forexample, on the slopes of arid places or waste lands, it has an effectof preventing falling of soils and sands and vegetation materials by thenet and provides a satisfactory function of supplying water.

In the steric structure net, according to the invention the stringportion is constituted into a steric shape having air transmittable andwater transmittable gap spaces with front and back fabric portionsknitted at a width for one or plurality of wales respectively by warpknitting and connecting yarns for connecting both of the fabricportions, and the string portion is continuous in the knitting directionand knotted alternately with string portions which are in continuous onboth sides in the front and back string portions respectively.

In this invention, not only satisfactory air transmittability and watertransmittability can be ensured by the steric structure of the stringportion defining the net mesh but also the water retention agent can bedeposited concentrically by utilizing fine gap spaces and large surfacearea formed by knitting the front and back fabrics of the stringportion. Therefore, the water absorption and water retention by thewater retention agent, combined with the water retention by the assemblyof the fibers, can increase the water retention as the entire net and,also in combination with the steric string portion that serves as thewater supply channel, can provide a further excellent function of watersupply.

Further, it is possible to use a steric structure net in which stringportion formed by the front and back fabric portions and the connectionyarns is knotted with adjacent string portions at the front and backfabric portions on every predetermined pitch in the continuing directionwhile being positionally displaced from each other, and the portions ofthe connection yarns for connecting the front and back fabric portionsin each of the string portions are alternately inclined rightwardly andleftwardly to form a truss structure.

In this case, when load and pressure exert on the net in the directionof the thickness, they act so as to regulate the turning-down of thestring portions to each other and the shape of the net mesh and thesteric structure of the net are stabilized. That is, it is strong to theload and pressure in the direction of the thickness, excellent in thepressure resistance and shape retainability and has good. elastic force.Accordingly, also when it is buried and used underground, the stringportion is not collapsed but keeps a steric state to possess asatisfactory water supply function.

Furthermore, even if a net mesh of a relatively large opening is formed,since the ratio of area occupied by the string portions is considerablylarge for the entire net in average and the surface area for the yarnsconstituting the net is also large, a great amount of the waterretention agent can be deposited and retained by so much to furtherenhance the water retaining effect.

In the steric structure net in each of the inventions, the yarns formingmesh at least in the front and back fabric portions are suitablycomprised of a plurality of aligned monofilament yarns, multifilamentyarns of synthetic resin or yarns comprising a combination of them.

That is, since the fiber density for the front and back fabric portionsof the string portion is increased by the constitution described aboveand, although this is a net, the water retention agent or the adhesivecontaining the water retention agent deposited by the coating means suchas dipping intrudes as far as the inside of the string portion and isdeposited so as to wrap the constituent yarns, the water retention agentcan be retained more stably. Particularly, the retention of the waterretention agent is satisfactory in a state of absorbing water andswelling to increase the volume. Therefore, if it is used being laid onthe slopes or buried underground, the water retention agent is notfallen easily.

Further, it may have a constitution in which a string portion not havingconnection yarns is provided so as to form a mesh opening smaller thanthat of the string portion having connection yarns for defining the netmesh opening space, in at least one of the front and back fabricportions in the steric structure net.

In this steric structure net, bending deformation or the like of thestring portion defining the net mesh opening space can be restricted bythe string portion not having the connection yarns, by which the stericstate of the string portion defining the net mesh opening space and theshape of the net mesh opening space can be retained more preferably.

In each of the inventions, the water retention agent is preferablydeposited to the net by a coating means such as dipping. For example,the water retention agent is mixed with a volatile solvent, water orother additive and deposited by coating to the net before it issolidified.

With such a constitution, the water retention agent can be depositedsurely to the yarns constituting the net and retained without droppingeasily during use and satisfactory water retentivity can be kept for along period of time.

Further, the retention agent can also be mixed with an adhesive anddeposited to the net by the coating means. As the adhesive, use of anaqueous adhesive is preferred with a view point for the effect of thewater absorbing and water retaining effect.

In this case, even if the net constituting yarns are made ofmonofilaments of synthetic resin, the water retention agent is surelydeposited and maintained by the adhesive and the water absorbing andwater retaining property can be maintained satisfactorily for a longperiod of time.

Further, due to the deposition of the adhesive, binding strength betweenthe yarns constituting the net is increased, stitches are less tend tobe slackened, the steric structure is more stabilized, the elastic forceand the compression resistance are increased, and the steric shape ofthe string portion defining the net mesh opening can be kept more easilyeven when the net mesh opening are formed to be large, so that the netmesh opening space is maintained in the steric shape and roots of plantsextend easily through the net meshes.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic plan view illustrating one embodiment of thepresent invention.

FIG. 2 is an enlarged perspective view for a portion thereof.

FIG. 3 is an enlarged cross sectional view for a portion thereof.

FIG. 4 is a view for a lapping state illustrating a concrete example ofa knitted tissue of a steric structure net.

FIG. 5 is a view for a lapping state illustrating another concreteexample of a knitted tissue of a steric structure net.

FIG. 6 is a schematic plan view illustrating another embodiment.

FIG. 7 is a schematic plan view illustrating a further embodiment.

FIG. 8 is a schematic perspective view illustrating a furtherembodiment.

FIG. 9 is a schematic perspective view illustrating a still furtherembodiment.

FIG. 10 is a cross sectional view in a case of use as a water supply netin a desert area.

BEST MODE FOR CARRYING OUT INVENTION

Next, the mode of practicing the present invention is to be explainedwith reference to the drawings. FIG. 1 shows an appearance of oneembodiment of a water retention net (A) comprising a truss type steric,or three-dimensional structure net which is warp knitted, for example,with synthetic fiber yarns, FIG. 2 shows an enlarged perspective viewfor a portion thereof and FIG. 3 is an enlarged cross sectional view.

In the drawing, (1) indicates a string portion defining a net meshopening (2), and (3) and (4) indicate, respectively, front and backfabric portions each in a net shape. (5) indicates connection yarns as aconnection portion between the front and back fabric portions (3) and(4). The string portion (1) is formed as a steric shape substantiallyhaving gap spaces which are air transmittable and water transmittable inthe longitudinal direction, as well as in the inside to outsidedirection through gaps between each of a number of the connection yarns(5) and (5) by connecting the front and back fabric portions (3) and (4)by laying the connection yarns (5) across both of them. (8) indicates aninternal space. (10) indicates a water retention agent deposited asdescribed later.

The water retention net (A) in the embodiment of FIG. 1 to FIG. 3 iswarp knitted by a double raschel machine having two rows of needle basesand basically comprises the front and back fabric portions (3). and (4)knitted by chain knitting yarns and insertion yarns, and connectionyarns (5) connecting the front and back fabric portions (3) and (4), inwhich the front and back fabric portions (3) and (4) are knitted and incontinuous in one direction. Each of the front and back fabric portions(3) and (4) is knotted with adjacent string portion on everypredetermined pitch in the knitting direction to constitute a stericstructure net. Particularly, the knot portions (6), (7), or joiningportion, in the front and back fabric portions (3) and (4) arepositionally displaced from each other between the front and back andthe connection yarns (5) for the string portion (1) are alternatelyinclined rightwardly and leftwardly to form a truss structure.

That is, the front and back fabric portions (3) and (4) of the stringportion (1) have a width for a plurality of wales as shown in anenlarged scale in FIG. 2 and FIG. 3 (three wales in the figure), andconnection yarns (5) are laid across and knitted in at least two waleson both side ends (all wales in the figure) between the front and backfabric portions (3) and (4), whereby the string portion (1) of asubstantially hollow steric shape having a space (8) between each of theconnection yarns (5) and (5) is continuously constituted in the knittingdirection.

Further, each of the string portions (1) is knotted with adjacent stringportions (1) on both sides alternately at the front and back fabricportions (3) and (4) at different positions by different knot insertionyarns respectively, that is, such that the knotting portion 6 at thefront and the knot portion (7) at the back are positionally displacedfrom each other. Whereby the portion of the connection yarns (5) arealternately inclined rightwardly and leftwardly on every predeterminedpitch in the continuing direction of the string portions (1) forming atruss structure in which the net mesh opening (2) is in a substantiallyV-cross sectional shape or inverted V-cross sectional shape.

FIG. 4 shows one example of a knitted tissue of the truss type stericstructure net. In the figure, (L3), (L2) and (L1) indicate a chainknitting reed, an insertion yarn reed and an insertion yarn reed forknotting, on the front. (L5), (L6) and (L7) indicate a chain knittingreed, an insertion yarn reed and an insertion yarn reed for knotting, onthe back. (L4) indicates a reed for connection yarns.

According to the knitted tissue diagram, on the front side, the frontfabric portion for each of string portions is knitted by stitch rows forthree wales by the chain knitting reed (L3) and the insertion yarn reed(L2), and the front fabric portions of adjacent string portions arealternately knotted rightwardly and leftwardly for one or plurality ofcourses by shifting knitting yarns for knotting inserted under lateralswinging by other insertion yarn reed (L1) alternately rightwardly andleftwardly on every predetermined pitch of courses. on the back side,back fabric portion of each of the string portions is knitted by thechain knitting reed (L5) and the insertion yarn reed (L6) respectively,and the back fabric portions for the string portions are knotted for oneor several courses by shifting the insertion yarns for knotting insertedunder lateral swinging by other insertion yarn reed (L7) to the rightand left sides opposite to that on the front side on every course pitchcorresponding to the knot portions on the front fabric portion. Then,the connection yarns are laid across the front and back fabric portionsat each wale of the string portion and connecting them, by an entiregathering reed (L4).

Further, FIG. 5 indicates other knitted tissue of a steric structure netin which (L1), (L2) and (L3), (L4) indicate insertion yarn reeds andchain knitting reeds on the front, (L6), (L7) and (L8), (L9) indicatechain knitting reeds and insertion yarn reeds on the back and (L5)indicates a reed for connection yarns.

In this knitted tissue, on the front side, each of the front fabricportions of the string portions are knitted by stitch rows for two walesby the chain knitting reeds (L3), (L4) and the insertion yarn reeds(L1), (L2), respectively, and knotted with the front fabric portions ofthe adjacent string portions on right and left sides by laterallyshifting the chain knitting reeds (L3), (L4) alternately rightwardly andleftwardly by two wales on every predetermined course corresponding tothe net mesh opening and then returned to the original position. On theback side, the back fabric portions of the string portions for two walesare knitted by the chain knitting reeds (L6), (L7) and the insertionyarn reeds (L8), (L9), and knotted alternately with the back fabricportion of the adjacent string portions on right and left side bylaterally shifting the chain knitting reeds (L6), (L7) by two walesalternately rightwardly and leftwardly opposite to the front side, onevery predetermined course, and then returned to the original position.Then, the connection yarns are laid across the front and back fabricportions for connection at each wale of the string portion, by an entiregathering reed (5).

After knitting the tissue as described above, the knitted fabric isproperly widened to take a form of a net or mesh, and heat setting isapplied so as to properly open the net mesh opening (2). Thereby theyarns used are provided with an appropriate rigidity and shape retainingforce.

The knitted tissue described above merely shows an example of the stericstructure net and it is not restricted only thereto but can be practicedby using various steric structure nets.

For example, by properly changing the number of courses (pitch) fordisplacing the positions of the front and back knot portions (6), (7)from each other, front and back knot portions (6), (7) may bepositionally displaced slightly from each other, for example, as shownin FIG. 6.

Further, the knotting length in the wale direction of the knot portions(6), (7) of the front and back fabric portions (3), (4) is notnecessarily identical, but it may be practiced, for example, as shown inFIG. 7 such that the knotting length of the knot portions (6), (7), thatis, the number of the knotting courses may be different between thefront and back sides of the fabrics. Further, a net mesh opening asshown in FIG. 8 can be constituted by substantially aligning thepositions for knot portions (6), (7).

Further, it may also be practiced by forming the net mesh openingsdifferent in the size between the front and back sides and,particularly, as shown in FIG. 9, a string portion (1 a) not havingconnection yarns (5) so as to form a mesh opening (2 a) smaller than thenet mesh opening (2) defined by the connection yarns (5) included in thestring portion (1) can be disposed to at least one of the front and backfabric portions (3) and (4). In this case, it is also possible tosatisfactorily maintain the shape of the string portion (4) and the netmesh opening space and retain other material in the net mesh openingspace.

In each of the embodiments, the string portion (1) may be provided witha width of four or more wales (usually, 2 to several tens wales) ormerely constituted with a stitch row of one wale.

While yarns used for the steric structure net is not particularlylimited and synthetic fiber yarns of excellent water proofness areusually used. Multifilament yarns or monofilament yarns of various kindof synthetic fibers such as nylon yarn, carbon fiber yarn are preferablyused in view of durability or the like. In a case of increasing thefiber density to improve the retentivity of the water retention agent,an aligned yarns of a plurality of monofilament, multifilament yarns oryarns comprising a combination of them may be used. Yarns of naturalfibers or yarns of biodegradable fibers can of course be used, which canprovide water retention nets gentle to environments.

The connection yarns (5) are properly selected from synthetic fiberyarns or natural fiber yarns while considering elasticity, strength orthe like in the foregoings such that they are suitable to connect andsterically support the front and back fabric portions (3) and (4).Mainly monofilament yarns are preferably used with a view point ofretaining the steric structure, while a plurality of yarns may be usedin combination.

The yarns may be provided properly with rigidity or compressionstrength, by heat setting or synthetic resin finishing after knitting.The diameter and the material for the yarns are determined whileconsidering the strength, tension and elasticity required depending onthe uses.

For example, in a case of use as a net for stabilizing slopes bygreening, there are used yarns of 100 to 5000 denier, preferably, 200 to1000 denier for the front and back fabric portions, and yarns of 100 to5000 denier more preferably, 200 to 2000 denier for connection yarns.

Then, in the water retention net (A) of the present invention, a waterabsorbing resin or a water retention agent mainly comprising the waterabsorbing resin is deposited substantially over the entire area at leaston one side of the steric structure net.

As the water retention agent, those resins generally known as waterabsorbing resins, for example, acrylic acid grafted starch, vinylalcohol—acrylic acid block copolymer, crosslinked acrylic acid, modifiedpolyvinyl alcohol or the like which absorb and retain a great amount ofwater upon contact therewith can be used preferably.

Further, as the water retention agent, those resins having waterabsorbability used generally as a thickening agent can be used by beingprovided with water retentivity by utilizing crosslinking reaction orthe like.

For example, a copolymer of N-vinylacetoamide and sodium acrylatedeveloped as a thickening agent (GE-167, manufactured by Showa DenkoCo.) can be used by adding epoxy compounds so as to utilize crossinkingby the epoxy compounds. Thus obtained water retention agent is resistantto salts, has high light fastness, and does not easily leach the waterabsorbing resin even after absorbing water. Thus, the water retentionagents preferably used. In particular, it possesses a sufficientdurability even in a use at a place near the seaside.

The water retention agent described above can be deposited to the net(A) by coating means utilizing the stickiness of the water retentionagent per se. In otherwise, after the water retention agent is mixedwith other additive and volatile solvent or water, the stickiness tillit is solidified is utilized. The water retention agent, when used inadmixture with ethylene glycol, can be provided properly with softnessand flexibility in a state deposited to the net and is not easilydetached by the movement such as extension or shrinkage of the net.

Further, also the water retention agent comprising previously-describedwater absorbing resin can be deposited to the net in the same manner bya coating means. In otherwise, it is desirably deposited to the net (A)by the coating means after admixed with adhesive, in view of theretentivity of the water retention material. In this case, use ofwater-soluble or water-dispersible adhesives is particularly preferredin view of practical use since the water absorbing and retainingproperty are further improved.

The coating means may be a usual coating method such as applying orspraying, as well as a method of dipping, that is, immersing in asolution of the agent. Further, it is not only deposited by the coatingusing the adhesive described above only to the portions of the front andback portions (3) and (4) but also it may be penetrated by the coatingmeans as far as the intermediate portion in the direction of thethickness of the string portion (1) of the steric structure net anddeposited and retained thereto, or may be deposited on entire net by thecoating means.

Further, if it is coated at least on one side of the steric structurenet in a shrinked state to close the net mesh opening (2), it is easilycoated to the front and back fabric portions (3) and (4) and the waterretention agent can be retained satisfactorily. In particular, if eachof the front and back fabric portions (3) and (4) of the string portion(1) of the net are knitted with one or plurality of wale width, theadhesives can be deposited and retained more easily in spite of forminga net structure.

In addition, a hot melt type synthetic resin or adhesive may be coated,for example, to the net (A) and the powder of the water absorbing resinmay be deposited thereto.

Then, the water retention net (A) to which the water retention agent(10) is deposited and retained on the steric net structure as describedabove has satisfactory air transmittability and water transmittabilitysince the string portion (1) defining the net mesh opening (2) has airtransmittable and water transmittable gap spaces. Further, satisfactorywater retentivity can be provided by the water retention agent (10)deposited at least on one side even if the net constituting yarns aresynthetic resin monofilaments.

Therefore, in the vegetation treatment with an aim of protection andgreening stabilization, for example, of slopes it can provide an effectof collecting and draining water upon rainfall due to watertransmittability by the possession of gap spaces in the steric stringportion, is excellent in water retentivity and can provide a sufficientfunction of supplying water required for the growth of plants even in aplace tended to be dried and with little rainfall.

Further, as the measure for the greening treatment of the desert, whenthe net (A) of the present invention is buried and used in the desertsoil 20 as shown in FIG. 10, it can retain sufficient water retentivityand a function of preventing evaporation over a wide range, can supplywater for a wide range since the string portion serves as a water supplychannel, can easily control the amount of water supply and it can supplywater satisfactorily. In addition, it is not necessary to append othermaterial such as non-woven fabric on the net and can be used at areduced cost. Further, water can be economized by the water absorbingfunction and the evaporation preventive function by the water retentionagent.

In addition, since the net mesh opening space. of the steric structurenet is large enough, when the net is buried in or laid on the ground, itallows free passage of water upon leaching for flushing out salts in theground or rainfall water, so that salts can be flushed out easily withno clogging upon leaching thereby preventing occurrence of salt damagescaused by accumulation of salts.

In the case of a steric structure net, it is possible to use otherproperly water retaining or water absorbing materials such as waterretaining agent in pack, water retaining fibers, water absorbing fibers,water retention mat and water retention paste by inserting and retainingthem to the steric net mesh opening space or to the steric stringportion. Further, vegetation materials such as packaged chemicalfertilizers or seeds can be retained.

In the embodiment illustrated in the drawings described above,explanation has been to a case where the net is a steric structure netbut the present invention can also be practiced in usual warp knittednet not in a steric shape, by constituting a water retaining net bydepositing the same water retention agent as described above by the samemeans as described above to the string portion defining the net meshopening.

Also in the case of this net, deposition and retention of the waterretention agent are improved by using various kinds of yarns describedabove for the constituent yarns and forming stitches by warp knittingsuch that the string portion defining the net mesh opening has a widthof one or plurality of wales. Further, those knitted by using aplurality of aligned monofilament yarns, multifilament yarns or yarnscomprising a combination of them are preferred in view of satisfactorydeposition and retention of the water retention agent.

INDUSTRIAL APPLICABILITY

As described above, by the water retention net according to the presentinvention, both of usual nets and steric structure nets can be used asthe vegetation nets possessing satisfactory water retention notobtainable in the conventional nets and used in the vegetation treatmentfor the slopes in little rainfall places or in arid places, as waterretaining and supplying nets for greening stabilization of deserts or aswater retaining or supplying nets in greening of cities.

In particular, the steric structure nets have satisfactory airtransmittability and water transmittability due to the retention of gapspaces, have excellent water collecting and draining function and waterretaining function together. Further, it can be used more suitably tothe above mentioned application use for the desert area or the like dueto the effect of preventing salt accumulation, for example, by leachingtaking advantage of allowing free passage of water and salts by the netmesh opening space.

what is claimed is:
 1. A three-dimensional net formed by warp knittingcomprising: three-dimensional string portions each defining net meshopening spaces in the three-dimensional net and being continuous in aknitting direction and including a front-side fabric portion and aback-side fabric portion, each knitted at a width for one or a pluralityof wales by warp knitting, and connection yarns for connecting both thefront-side and back-side fabric portions with a gap therebetween,through which water and air are transmittable; and the front-side andback-side fabric portions of each three-dimensional string portion beingalternately joined with rightward and leftward adjacentthree-dimensional string portions at every predetermined pitch in theknitting direction, each of said front-side and back-side fabricportions having a knitting repeat pattern, the knitting repeat patternsof said front-side and back-side fabric portions being offset from oneanother by a half repeat, wherein: a position of the joining portion atwhich the front-side fabric portion of one three-dimensional stringportion is joined to the adjacent three-dimensional string portion isdisplaced along said one three-dimensional string portion from acorresponding position of the joining portion at which the back-sidefabric portion of said one three-dimensional string portion is joined tothe adjacent three-dimensional string portion; the connection yarnsbetween the front-side and back-side fabric portions of eachthree-dimensional string portion are alternately inclined leftward andrightward at every predetermined pitch in the knitting direction whileinclination of the connection yarns in every adjacent two of thethree-dimensional string portions are in a manner of offsetting eachother, so that the connection yarns extended from each of the joiningportions to rightward and leftward ones of the three-dimensional stringportions are in opposite inclinations to constitute a truss structure;and a thickness-wise stress applied onto the front-side or back-sidefabric portion is converted to a horizontal stress applied to back-sideor front-side fabric portion by way of the connection yarns inclinedleftward and rightward from each of the joining portion to resistcollapsing.